Every year Standard and Poors publishes a “scorecard” comparing active mutual fund managers to the indexes.  Every year it's pretty much the same story- active fund managers can't persistently beat a passive investment.  This year's version recently came out.  Here are the highlights:

1) From September 2009 to September 2012, 23.6% of large-cap funds, 15.5% of mid-cap funds, and 29.4% of small-cap funds remained in the top half with regards to fund performance (AKA beat a low-cost index fund.)  Random chance would lead to 25% of remaining in the top half for all 3 years.

2) From September 2007 to September 2012, 5.2% of large-cap funds, 3.2% of mid-cap funds, and 5.1% of small-cap funds remained in the top half for all 5 years.  Random chance would lead one to expect at least 6.25% would remain in that category.

In essence there is no persistence of performance.  You CANNOT choose an actively managed mutual fund based on past performance and expect that to persist in any way, shape, or form.  Actually, that's not entirely true.  There is some persistence of performance….among the bottom quartile funds.  They're much more likely to be merged or liquidated than better performing funds.

As one part of the study they took mutual funds that performed in the bottom half over a 5 year period and took a look at how they performed over the next 5 years.  For all US Domestic funds, those in the bottom half over the first 5 years had a 36.8% chance of being in the top half over the next 5 years, a 34.5% chance of being in the bottom half, and a 28.7% of disappearing completely. Now, I think it's safe to say that those that disappeared weren't doing well, so in reality 63.2% of bottom half funds stayed in the bottom half.

Moral of the story?  Good funds go bad and bad funds stay bad.  If the chances of you choosing a 5 year winner are only 1 out of 20, and you have to do this for 5 or 10 different asset classes, the odds of you designing an actively managed portfolio that will outperform a passively managed portfolio seem astronomically small.  Save yourself the trouble and buy low-cost index funds.